Two-way implementation of graphene nanoflakes in perovskite solar cells

Both the electron transport layer (ETL) and the hole transport layer (HTL) are critical for power conversion efficiency (PCE) and stability in inverted perovskite solar cells (PSCs). In recent years, graphene-related materials have been widely used as dopants for the ETL and HTL due to their numerous inherent superior properties. Common forms of graphene, such as reduced graphene oxide or graphene synthesized by high-temperature chemical vapor deposition (CVD), have demonstrated benefits for PSCs. However, a more ingenious implementation of high-quality graphene in PSCs is still awaiting further exploration. In this study, we conduct a comprehensive investigation of graphene nanoflakes (GNFs) grown using a plasma-enhanced CVD (PECVD) system to achieve dual functionality as a dopant in both the ETL and HTL. The GNFs can be synthesized using a relatively simple, clean, and efficient PECVD system compared to other graphene-related materials. More importantly, unlike in existing literature, the as-synthesized GNFs were incorporated into either NiO_x (the HTL), PC₆₁BM (the ETL), or both, to compare the resulting improvements in device performance. The optimized photovoltaic with GNF-doped buffer layer demonstrates a 17.4 % enhancement in PCE.